By HELENE COOPER

April 8, 2014

BEIJING — The United States and China clashed over Japan on Tuesday as the Chinese defense minister asserted that Beijing had “indisputable sovereignty” over a group of islands in the East China Sea and that his country’s military stood ready to protect its interests in territorial disputes.

The minister, Gen. Chang Wanquan, said that China would not be first to launch an attack over the territorial dispute. But he accused Japan of “confusing the right with the wrong” in its assertion of control over the disputed islands in the East China Sea, which are known as the Senkaku in Japan and as the Diaoyu in China.

“China has indisputable sovereignty over the Diaoyu Islands,” General Chang said. He added that on the issue of what he called “territorial sovereignty,” China would “make no compromise, no concession, no treaty.”

He continued, “The Chinese military can assemble as soon as summoned, fight any battle and win.”

General Chang made his comments at a news conference with the United States defense secretary, Chuck Hagel, after a morning of meetings at the Ministry of National Defense. It is Mr. Hagel’s first trip to China as defense secretary.

While both men sought to present their meetings as constructive, they espoused divergent views on a number of issues, particularly the territorial dispute in the East China Sea, and a similar dispute between China and the Philippines in the South China Sea.

At one point, Mr. Hagel appeared impatient, wagging his finger. “The Philippines and Japan are longtime allies of the United States,” he said. “We have mutual self-defense treaties with each of those countries,” he continued, adding that the United States was “fully committed to those treaty obligations.”

Defense Secretary Chuck Hagel at a news conference in Beijing on Tuesday with the Chinese defense minister, Gen. Chang Wanquan.

Pool photo by Alex Wong

Mr. Hagel accused China of adding to tensions in the region by declaring an air defense zone in the East China Sea with “no collaboration, no consultation.” Such moves, he warned, could “eventually get to dangerous conflict.”

The exchange punctuated a visit that American defense officials had sought to present as a long-awaited deepening of military relations between the countries. On Monday, Mr. Hagel became the first foreign dignitary allowed on board a Chinese aircraft carrier, and on Tuesday the United States and China announced modest steps toward improving communications.

But there appeared to be no closing of the gaps on more contentious issues.

Mr. Hagel, for instance, called on China to be more open about its cyberwarfare capabilities, which American officials have said Beijing uses for commercial espionage.

Mr. Hagel portrayed the United States as transparent about its own capabilities in telecommunications security, pointing to a recent briefing that the Defense Department gave to Chinese officials on the Pentagon’s doctrine for defending against cyberattacks. “More transparency will strengthen China-U.S. relations,” he said. “Greater openness about cyber reduces the risk that misunderstanding and misperception could lead to miscalculation.”

Beijing, American defense officials said, still has not responded to Mr. Hagel’s invitation to reciprocate with a briefing of its own.

General Chang stood impassively during Mr. Hagel’s call for more openness on cybersecurity. When it was his turn to talk, he said that “the defense activity of the People’s Liberation Army in cyberspace abides” by Chinese law. “It will not pose a threat to others,” he added.

The disagreement with China over digital security issues puts Mr. Hagel in the difficult position of arguing with Beijing over what is acceptable to spy on and what is not. American officials have maintained that a barrage of attacks that originated in China aimed at stealing technology and other intellectual property from Silicon Valley and from military contractors and energy firms in the United States. Many of those attacks have been linked to cyberwarfare units of the People’s Liberation Army, acting on behalf of state-owned, or state-affiliated, Chinese companies.

But the United States has not always been transparent about cyberespionage, either. Last month The New York Times and the German magazine Der Spiegel reported that the United States had infiltrated the networks of Huawei, China’s networking and telecommunications giant. Additional disclosures about American spying were revealed in National Security Agency documents leaked by Edward J. Snowden, a former contractor at the agency.

After his meetings at the Defense Ministry, Mr. Hagel went to the National Defense University in Beijing to give a speech and hold a question-and-answer session with about 120 Chinese military officers. Most of the questions from the audience centered on the Senkaku-Diaoyu dispute, as Chinese officers repeatedly complained that American policy in the region favored Japan.

Late last year, China set off a trans-Pacific uproar when it declared that an “air defense identification zone” gave it the right to identify and possibly take military action against aircraft near the islands. Japan refused to recognize China’s claim, and the United States has since defied China by sending military planes into the zone, unannounced.

In February, Capt. James Fannell, the director of intelligence and information operations with the United States Pacific Fleet, said in San Diego that China was training its forces to be capable of carrying out a “short, sharp” war with Japan in the East China Sea.

The dispute over the islands also figured prominently on Tuesday at the New York debut of the Asia Society Policy Institute, a nonpartisan research group created by the Asia Society. China’s ambassador to the United States, Cui Tiankai, participating in a panel on Asian peace and prosperity, politely but firmly warned the United States about taking sides with Japan.

Without identifying Japan by name, Mr. Cui said America should think hard about whether its military alliances with other countries in Asia were serving American interests. He also rejected the idea of settling the island dispute through arbitration, challenging the United States to put itself in China’s position.

“I don’t think the United States would subject itself to any international arbitration when its sovereignty and territorial integrity is concerned,” he said. “Most probably you would send out an aircraft carrier task force there. We are not doing that — yet.”

William J. Burns, the deputy secretary of state, said in a keynote speech at the event that the island dispute and North Korea’s bellicose behavior were the two most serious security issues facing Asia. Mr. Burns also sought to allay concerns that the Obama administration was wavering in its so-called “pivot to Asia” because of crises elsewhere in the world. Going forward, Mr. Burns said, “no region will be more consequential for American interests and for the shape of the global system than the Asia Pacific.”